1. Field of the Invention
The present invention relates an actuator for use in electronic devices, a method of controlling the actuator, and a switch including the actuator.
2. Related Art
A conventional actuator of a micro-electro-mechanical system (MEMS) is disclosed in Japanese Patent Laid-Open Publication No. 2000-188050. The actuator includes an arm having an elastic property, and is supported on a substrate. A positive voltage is applied to one of respective electrodes provided on the substrate and the arm, and a negative voltage is applied to the other of the electrodes, thereby producing an electrostatic force. This electrostatic force causes the arm to deform toward the substrate. A movable contact provided on the arm accordingly contacts a fixed contact provided on the substrate, thus allowing the actuator to operate as a switch.
In this actuator, the distance between the electrostatic electrodes becomes the largest at an initial position in which the arm is straight. In order to drive the arm at a high speed from the initial position, a large electrostatic force is required, thus requiring an increased a voltage applied to the electrodes. The deforming arm returns by an elastic force after the electrostatic force is released, and a speed of return is limited.
Another conventional actuator includes an arm deforming by a piezoelectric drive. In this actuator, when a movable contact contacts a fixed contact, the arm may vibrate, accordingly generating a noise.
While being used as micro-switches, conventional actuators of MEMS have not be able to be used in a switch required to have a large driving speed, such as a switch for switching the connection of transmitting and receiving signals of a portable telephone.